1. Field of the Invention
The present invention relates to satellite systems, and, more particularly, to waveguides for use with satellite systems.
2. Description of the Related Art
A waveguide is a device which constrains or guides the propagation of electromagnetic waves along a path defined by the physical construction of the waveguide. More specifically, a waveguide usually includes a metallic tube which can confine and guide the propagation of electromagnetic waves in the lengthwise direction of the tube. In satellite systems, a waveguide is used as a conduit for the transmission of communication signals between the feedhorn of a satellite dish and the electronics of the satellite system, such as a transceiver. A satellite dish and associated feedhorn are typically placed outdoors. Consequently, portions of the waveguide which lead to the feedhorn may also be located outdoors.
It is known to substantially seal a waveguide to prevent outside moisture from entering and condensing within the waveguide. Water droplets within a waveguide can cause corrosion and signal losses resulting in an unacceptable degradation in performance. It is also possible for water within a waveguide to damage the system electronics.
A problem with conventional waveguides is that moist air still sometimes penetrates a waveguide and condenses therein. This penetration of moist air into the waveguide may occur when the outside atmospheric pressure undergoes a relatively sudden increase. The inside of the waveguide remains at the former lower atmospheric pressure. Hence, the pressure difference between the outside and the inside of the waveguide may force air from the outside, which can be moist, through any small cracks or holes in the waveguide. Such small openings in the waveguide can be otherwise airtight under normal pressure conditions.
It is also known to pressurize the inside of a waveguide with a mechanical air pump in order to inhibit ambient air from entering the waveguide. A problem is that air will leak out of the pressurized waveguide into the ambient environment, just as air penetrates the waveguide as described above when ambient pressure is higher than pressure within the waveguide. As air leaks out of the waveguide over some period of time, pressure within the waveguide substantially equalizes with ambient pressure. When ambient pressure eventually rises, ambient air may again be forced into the waveguide, causing the same problems discussed above. For this reason, the waveguide must be repressurized rather frequently.
It is further known to provide a waveguide with a port or hole fluidly connected to a bottle containing a desiccant or drying agent for dehumidifying the air within the waveguide. The bottle contains a single opening which is fluidly connected with the waveguide port. A problem is that the desiccant can relatively quickly become saturated with moisture from the air within the waveguide. When saturated, the desiccant no longer effectively absorbs moisture from the air within the waveguide and must be replaced often, or at least dried out for subsequent use.
What is needed in the art is a waveguide which inhibits moist air from entering therein, even under extreme atmospheric conditions, and does not need frequent maintenance.